Dimethyl ether reaction kinetics at high temperature were studied in two different flow reactors under highly dilute conditions. Pyrolysis of dimethyl ether was studied in a variable-pressure flow reactor at 2.5 atm and 1118 K. Studies were also conducted in an atmospheric pressure flow reactor at about 1085 K. These experiments included trace-oxygen-assisted pyrolysis, as well as full oxidation experiments, with the equivalence ratio (ϕ) varying from 0.32 ≤ ϕ ≤ 3.4. On-line, continuous, extractive sampling in conjunction with Fourier Transform Infra-Red, Non-Dispersive Infra-Red (for CO and CO2) and electrochemical (for O2) analyses were performed to quantify species at specific locations along the axis of the turbulent flow reactors. Species concentrations were correlated against residence time in the reactor and species evolution profiles were compared to the predictions of a previously published detailed kinetic mechanism. Some changes were made to the model in order to improve agreement with the present experimental data. However, the revised model continues to reproduce previously reported high-temperature jet-stirred reactor and shock tube results. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet: 32: 713–740, 2000

The reaction kinetics of dimethyl ether. I: High‐temperature pyrolysis and oxidation in flow reactors

The structure of a near-sooting flat low-pressure laminar benzene-oxygen-argon flame was studied using a molecular beam mass spectrometer system. Mole fraction profiles of fifty-one species are presented and their mechanistic implications are discussed with regard to the decay of benzene and the formation of polycyclic aromatic hydrocarbons and soot. A mechanism is outlined for production of C 2 , C 3 , C 4 and C 5 species from initial attack of O atom on benzene. Trends observed as the fuel equivalence ratio is increased past the sooting limit suggest a sequential growth from polycyclic aromatic hydrocarbons of 120–210 amu to heavier species and then to soot. A critical step in mechanisms for rapid growth of aromatic structures by free radical addition reactions is the stabilization of the adduct by forming six-membered rings. A mechanism requiring methyl substitution on the aromatic ring is discussed.

Composition profiles and reaction mechanisms in a near-sooting premixed benzene/oxygen/argon flame

A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 02 < 0 < 25, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 10 and 650 :5 T :5 1300 K The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (eg the primary reference fuels, n-heptane and iso- octane) under similar conditions The numerical model consists of 78 chemical species and 336 chemical reactions The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM

/pdf/a-wide-range-modeling-study-of-dimethyl-ether-oxidation-2w5vtl2qna.pdf

A wide range modeling study of dimethyl ether oxidation

A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.

/pdf/wide-range-modeling-study-of-dimethyl-ether-oxidation-pnag57ojwu.pdf

Wide range modeling study of dimethyl ether oxidation

The objective of this series of investigations is to develop procedures for predicting thermodynamically consistent generic rate rules for abstraction, addition, and isomerization reactions based o...

Reaction Rate Prediction via Group Additivity, Part 2: H-Abstraction from Alkenes, Alkynes, Alcohols, Aldehydes, and Acids by H Atoms

Kinetic isotope effects in the reactions of hydrogen and deuterium atoms with dimethyl ether and methanol

It is pointed out that the investigated reaction of oxygen with dimethyl sulfide may play an important role in photochemical smog formation and in the chemical evolution of dense interstellar clouds. Kinetic data were obtained with the aid of the flash photolysis-resonance fluorescence method. The photodecomposition of molecular oxygen provided the oxygen atoms for the experiments. The decay of atomic oxygen was studied on the basis of resonance fluorescence observations. Both reactions investigated were found to be fast processes. A negative temperature dependence of the rate constants for reactions with dimethyl sulfide was observed.

Absolute rate parameters for the reaction of ground state atomic oxygen with dimethyl sulfide and episulfide

The kinetics of the gas phase reactions of H (and D) atoms with benzene were investigated using fast flow techniques. Specific rate constants were obtained using two separate systems, one with ESR detection to monitor the decrease in atomic reactants and the other with mass spectrometry to follow the change in benzene concentration. The results from these two systems are in essential agreement with one another when discussed in the light of the proposed reaction mechanisms. The mass spectrometric studies lead to a recommended specific rate constant of (5.7 ± 1.0) × 1010 cm3 mole−1 · sec−1 at 300°K for the H+C6H6 reaction. The activation energies for the D and H atom reactions with C6H6 are equal, within experimental error, with the value of 2.70 ± 0.20 kcal/mole reported. For reasons discussed in this paper, it is concluded that this activation energy refers to the addition of the atomic reactant to the benzene ring. Since isotopic exchange reactions have been observed in these systems, the over‐all rate ...

Kinetics and mechanism of the reaction of hydrogen and deuterium atoms with benzene and benzene‐d 6

The kinetics of the reaction of O(3P) atoms with acetone were investigated using fast flow methods. The reaction was studied over a temperature range of 298 to 478°K. The specific rate constant obtained was (1.9 ± 0.4) × 1012 exp(—5040 ± 180/1.987 T) cm3/mol·sec. The observation of a sizable primary H/D kinetic isotope effect in comparing rates of CH3COCH3 and CD3COCD3 led to the conclusion that the major reaction channel involves H atom abstraction, namely, 








The rather low Arrhenius preexponential factor obtained in this reaction is compared and contrasted with those reported for other reactions of O(3P) with low molecular weight compounds.

J. H. Lee

Papers

Kinetic isotope effects in the reactions of hydrogen and deuterium atoms with dimethyl ether and methanol

Absolute rate parameters for the reaction of ground state atomic oxygen with dimethyl sulfide and episulfide

Kinetics and mechanism of the reaction of hydrogen and deuterium atoms with benzene and benzene‐d 6

Kinetics and mechanism of the gas‐phase reaction of O(3P) atoms with acetone

Absolute rate parameters for the reaction of ground state atomic oxygen with dimethyl sulfide and episulfide